Composition for use in preparing metal for a deforming operation and method of deforming



nited rates No Drawing. Application April 28, 1953 Serial No. 351,728

6 Claims. (Cl. 148--6.i5)

This invention relates to the art of deforming metal and is particularlyconcerned with the provision of an improved composition for use in thisart as Well as to an improved method. We treat and prepare the surfaceof a metal piece prior to mechanically working the same by suchoperations as are involved in drawing, rolling, stamping or otherwisealtering the physical shape of the piece.

The invention is especially useful in the treatment and working offerriferous metals and Will be described with this specific field ofusefulness in mind.

The mechanical working of ferriferous metal articles by processes thatare known as cold processes has come to be of steadily increasingimportance and many of such processes include the step of producing onthe metal surface a crystalline phosphate coating followed by theapplication thereto of various lubricants prior to the actual step orsteps of deformation. As is well known in the art, where suchphosphatizing procedures have been employed, it has generally beencustomary to make use of solutions which produce on ferriferous surfacesrelatively heavy non-metallic coatings consisting principally of Zinc ormanganese phosphate. Subsequent to this step, it has heretofore beennecessary to rinse the phosphatized surface and then to impregnate therinsed surface With lubricant prior to the actual deforming operation.This procedure, of course, results in a somewhat laborious multi-stepprocess, the usefulness of which has been severely limited in certainfields of activity, especially in plants or mills which are designed forrelatively high speed manufacturing procedures or where limited space isavailable.

With the foregoing in mind, the principal objects of our invention willbe better understood and they may be said to involve the provision ofnew compositions for use in treating a metallic surface prior to theactual deforming operation, which compositions materially shorten thetime involved without in any way sacrificing the many advantagesincident to the previous but somewhat more laborious procedures which,heretofore, as stated, have involved the steps of initial phosphatecoating, rinsing and final lubrication prior to deformation. Anotherobject of our invention is the provision of a lubricated crystallinephosphate coating for the purpose described, which coating is lesssusceptible to being stripped from the surface during the deformingoperation which, of course, gives rise to a marked advantage in the factthat it affords a safety factor in the maintenance of a continuouslubricant film, thereby mitigating the possibility of damage either tothe article being deformed or to the die or other tool being used in thedeforming operation Additionally, our invention makes it possible tosubject the article to a series of deforming operations with lessnecessity for frequent rephosphatizing and lubricating operations. Astill further object is to reduce the power required to accomplish agiven deformation.

The foregoing, together with such other objects as may appearhereinafter or are incident to our invention, are

attained by means of the invention now to be described. We havediscovered that certain saturated fatty acids having at least 12 carbonatoms may be emulsified in an acid phosphate coating bath without in anyway interfering with the deposition of the crystalline phosphate coatingon the metallic surface. Examples of such acids are stearic, myristic,lauric, palmitic, etc. This makes it possible to provide a bath by meansof which simultaneous phosphatizing and lubrication of the metallicsurface may be accomplished as a one-step procedure. The straight chain,fatty acids may be used by themselves or in conjunction with theirglycerides for certain special purposes which will be pointed outhereinafter.

Briefly stated, our invention involves the use of a conventional acidphosphatizing bath (preferably, although not necessarily, a zinc ormanganese phosphatizing bath), which bath may or may not containaccelerators and which has emulsified therein from 0.10 to 5% (weight/volume on the conventional grams/ cc. basis) of a saturated straightchain fatty acid having at least 12 carbon atoms. Phosphatizing bathscapable of producing a crystalline phosphate coating, of course, arevery well known to the art and need not be particularly described. Inour invention the fatty acids are emulsified therein generally by addingto the bath an amount of an emulsifying or dispersing agent, eithernon-ionic or cationic in character, sufiicient to disperse the fattyacid in the bath at the temperature of normal operation. Such emulsifiedbaths have been found to impart to ferriferous metal surfaces acrystalline phosphate coating while simultaneously impregnating thecoating with the lubricant in such fashion as to result in a surfacehaving optimum lubricity when subsequently dried and subjected tomechanical deformation.

According to the practice which we prefer, the quantity of lubricantemulsified in the bath lies between 0.25 and 1% (weight/volume on theconventional grams/ 100 cc. basis). Such quantity, we have found,produces exceptionally good results because at concentrations oflubricant of over 1%, there is sometimes a tendency for the phosphatecoated surface to be so impregnated with lubricant that there may be abuild-up of lubricant on the die or other tool. This is not always truefor some reason or other but we have found by experience that a 1% upperlimit is generally preferable. On the other hand, at lubricantconcentrations of less than 0.25%, the phosphate coated surface may nothave the maximum lubricity desired for certain deforming operations and,at concentrations of less than 0.10% of lubricant, the lubricity of thecoatings falls oif markedly. At concentrations greater than the 5% oflubricant, mentioned above as a maximum, there may be an interference ofthe lubricant with the formation of satisfactory phosphate coatings.While our preferred practice is to employ either zinc or manganesephosphatizing solutions, as indicated above, yet it should be noted thatany acid phosphatizing solution which is capable of producing acrystalline phosphate coating on the metal surface may be employed.

With our invention it is sometimes desirable to add to the bathglycerides of the fatty acids employed. The reason for this is asfollows. In certain difiicult operations, such as upset drawing,contrary to prior practice, the dies will run so cold, because of thehigh degree of lubricity imparted to the metal by our invention, thatthe presence of glycerides, by virtue of their relatively low meltingpoint, will permit the part being deformed to be easily ejected evenwhen cold. Where use of glycerides is indicated we prefer to replace aportion of the fatty acid with the glyceride and this can be done up toapproximately 25% of the fatty acid.

By way of specific example, the present invention may 3 be carried outin the following way. First, a typical concentrated phosphatizingcomposition may be prepared as follows:

V Formula.A Zinc oxide; pounds 2.43 Phosphoric acid,.75% r gallons 0.263Nitric acid, 56.5% do 0.426

Water, to make 1 gallon.

A phosphatizingbath may be prepared from the foregoing by dilution withsufficient water to make a con ventional 3% byvolum'e phosphatizing bathand this bath, of course,. will be nitrate accelerated because of thepresence of the nitric acid.

Next, an emulsion of 'the following formula is pre- Suflicicnt of theforegoing lubricant emulsion composition is then added to such aphosphatizingbath in a quantity which will yield approximately a 1%concentration of the lubricant emulsion inthe bath. The piece to betreated and deformed is then subjected to the action of such anemulsified bath. The solutions may be used in any conventional manner,i. e., in dip baths or in spray processes or 'in any other way by meansof which the surface of the metal is thoroughly contacted with theliquid for a sufficient length of time to allow for the formation of acrystalline phosphate coating. The time involved will depend, of course,upon the temperature of the bath and other factors familiar to thoseskilled in the art of phosphate coating but, as a general rule, asatisfactory coating will .be produced in anywhere from one to fiveminutes. When the phosphate coating is formed it will be foundthat thelubricant will have acted thereon to form the-lubricated surfacedesired.

After removal from contact with the solution, it is necessary to dry thecoating before proceeding to the deforming operation. As a general rule,we prefer to adjust thetemperature of the drying operation so that thelubricant will notmelt and run because over-heating and running of thelubricant may cause the surface to lose some. of its lubricity. However,experiments have indicated that even in the case of over-heating, thecoating still has more lubricating value than it would have had had theobject been treated accordin'g'to prior practice, namely, to an-initialphosphate coating step followed by a lubricant impregnation step.

As stated previously, any acid phosphatizing solution capable ofproducing a crystalline phosphate coating may be used. One of the mostsimple baths of this nature prepared to embody our invention is asfollows:

Formula C Pounds Emulsifying a ent 0.15 Stearic acida 0.15 Phosphoricacid, 75% 0.15 Water 0.55

4 V thereon a highly satisfactory lubricated crystalline phosphatesurface having the advantages of the present invention.

in order to compare the results attained with our invention with theresults whichare characteristic of prior practice, work was treated'anddeformed in accordance with the foregoing instructions and exactlysimilar pieces were first treated in a bath prepared from Formula A, asgiven above, after which the pieces were subjected to the lubricatingemulsion of Formula B. In other words, the two-step procedure of theprior art was contrasted with the one-step procedure of our invention.Furthermore, various other conventional phosphate coating bathswereemployed in treating metal pieces, both in accordance with priorpractice and in accordance with the present invention. In all instances,the results obtained with the present invention were markedly superiorto the results attained by prior practice. Pieces processed and deformedin accordance with, our invention were less susceptible to having thecoating stripped from the surface being deformed' and repeateddeformation operations were possible without the necessity ofrephosphatizing and relubri'cating as frequently as such steps have beennecessary in the prior art. Furthermore, damage to the article itself orto the die or other tool was noticeably. diminished. It was alsodetermined by suitable tests wherein the power necessary to draw a steelbar through a die was measured, that the. drawing operation could beperformed in accordance with our invention with materially less forcethan was required where the practice of the prior art was followed. Iustwhy this should be is not fully understood but the fact remains that itconstitutesan additional advantage accruing from the use of ourinvention.

In addition to the advantages already noted, it is obvious that ourinvention will result in a saving in operating,

costs.

The emulsification can be accomplished in any desired manner familiar tothose skilled in the art of emulsification. In addition to the use ofeither non-ionic or cationic. emulsifying or dispersing agents, asmentioned above, certain more modern ultrasonic techniques maybe availedof, if desired. In other words, the manner in which the emulsificationis accomplished is not critical and the appended claims are not to beconstrued as being limited in this respect.

We claim:

1. A metal coating bath consisting essentially of an aqueous acidphosphate solution capable of producing a crystalline phosphate coatingon the surface of the metal, said bathhaving emulsified therein, as anaddition agent, from 0.10 to 5% (weight/volume on the conventionalgrams/ cc. basis) of a saturated straightchain fatty acid having atleast 12 carbon atoms.

2. The bath of claim 1 where the phosphate of the bath is chosen fromthe class of zinc and manganese.

3. The bath of claim-2 where the quantity of fatty acid lies between0.25 and 1%.

4. The bath of claim :1 in which not over 25% of the fatty acids isreplaced by glycerides of such fatty acids. 5. Inthe art of deforming .ametal piece by a drawing operation or the like, the method whichconsists in treat-' 5 References Cited in the file of this patent2,473,614

UNITED STATES PATENTS 1,895,320 Gravell Jan. 24, 1933 2,008,939 TuftsJuly 23, 1935 5 2,276,453 Bandur Mar. 17, 1942 496,866 2,357,342Montgomery Sept. 5, 1944 863,281

6 Snyder June 21, 1949 Snyder Aug. 16, 1949 Schuster et a1. Mar. 27,1956 FOREEGN PATENTS Great Britain Dec. 7, 1938 Germany Jan. 15, 1953

1. A METAL COATING BATH CONSISTING ESSENTIALLY OF AN AQUEOUS ACIDPHOSPHATE SOLUTION CAPABLE OF PRODUCING A CRYSTALLINE PHOSPHATE COATINGON THE SURFACE OF THE METAL, SAID BATH HAVING EMULSIFIED THEREIN, AS ANADDITION AGENT, FROM 0.10 TO 5% (WEIGHT/VOLUME ON THE CONVENTIONALGRAMS/100 CC. BASIS) OF A SATURATED STRAIGHTCHAIN FATTY ACID HAVING ATLEAST 12 CARBON ATOMS.